The adenyl cyclase of the cellular slime mold, Dictyostelium discoideum, will be characterized and the regulation of its synthesis and activity will be examined. A cyclic AMP-binding protein already isolated from the same organism will be purified and its interaction with homologous DNA and chromatin investigated. An enzyme which catalyzes the rapid phosphorylation in D. discoideum of endogenous protein(s) at O degrees C will be isolated and an attempt made to identify the substrate(s).